Wide band gap semiconductors such as a Group III nitrides offer a number of superior properties that make them very attractive for a number of electronic applications. In particular, high electric field breakdown strengths, high current carrying capabilities and high electron saturation velocities allow nitride-based High Electron Mobility Transistors (HEMTs) to provide very high voltage and high power operation at microwave and mm-wave frequencies.
In order to promote wide scale adoption of this technology, Group III nitride HEMTs must satisfy certain minimum power performance requirements and a minimum operation time duration before power degradation. One particular aspect that has limited the device performance and device lifetime has been the presence of high electric fields in these structures that lead to increased charge trapping and excessive gate leakage. These field dependent mechanisms can be significant obstacles to achieving the required device performance and stability.
It would be desirable to have a semiconductor device fabrication process that could minimize field dependent degradation mechanisms and enable the manufacture of HEMT devices suitable for reliable microwave and mm-wave frequency operation. It would be further desirable for such a semiconductor fabrication process to also satisfy the production efficiency and complexity levels of current semiconductor device fabrication processes. It would be further desirable for such a semiconductor fabrication process to have repeatability and robustness in a manufacturing environment.